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Len'z Law
This Really Sucks Wikipedia Doesn't Allow XHTML, or HTML :\ I was hoping to put some java here or flash animations. Biography Heinrich Friedrich Emil Lenz was Russian physicist who in 1833 formulated Lenz's law, a fundamental law of electromagnetism. He also found that the strength of a magnetic field is proportional to the strength of the magnetic induction. Lenz's studies of electromagnetism date from 1831. He is best-known for Lenz's law, which he discovered in 1834 while investigating magnetic induction. The Lenz's law in electromagnetism is a statement that an induced electric current flows in a direction such that the current opposes the change that induced it. The Resistance In 1833 Lenz reported investigations into the way electrical resistance changes with temperature, showing that an increase in temperature increases the resistance (for a metal). Lenz also studied the relationship between heat and current and discovered, independently of English physicist James Joule, the law now known as Joule's law, which shows that heating effects accompany the flow of electricity in conductors. His Death In August, 1864, Lenz went to Italy for medical reasons, but he later died on February 10, 1865, in Rome after suffering a stroke. Introduction ''Magnetic Forces'' :: Right Hand Rule Number One :: Right Hand Rule Number Two We've learned that there are two right hand rules that will help us find the direction of the Magnetic Force. Heinrich Lenz discovered a third right hand rule that will help us find the direction of Magnetic Force. Right Hand Rule One, and Right Hand Rule Two have not specified which direction the emf(electro magnetic field) generated by a time varying magnetic flux linking an electric circuit acts. Thus we need a '''Right Hand Rule Number Three. The Law Suppose that a current I''' circulates around a planar loop of conducting wire and, thereby, generates a magnetic field '''B. What is the direction of this magnetic field as it passes through the middle of the loop? Well, if the fingers of my right-hand circulate in the same direction as the current then the thumb of my right-hand indicates the direction of the magnetic field as it passes through the centre of the loop. This is illustrated in the diagram below. Lenz's law The Theory General Consider a plane loop of conducting wire which is linked by magnetic flux. By convention, the direction in which current would have to flow around the loop in order to increase the magnetic flux linking the loop is termed the positive direction. Likewise, the direction in which current would have to flow around the loop in order to decrease the magnetic flux linking the loop is termed the negative direction. Suppose that the magnetic flux linking the loop is increased. In accordance with Faraday's law, an emf is generated around the loop. Does this emf act in the positive direction, so as to drive a current around the loop which further increases the magnetic flux, or does it act in the negative direction, so as to drive a current around the loop which decreases the magnetic flux? It is easily demonstrated experimentally that the emf acts in the negative direction Demonstration A loop of wire is moved back and forth through a region of uniform magnetic field (yellow). The magnetic field is perpendicular to the page. An induced current (red) is produced in the directions indicated by the arrow according to Lenz's Law. Sample Questions Test Reference Resources